1. Field of the Invention
The present invention relates to a microscope apparatus capable of carrying out time-resolved spectroscopy in a minute region under microscope observation.
This application is based on patent application Nos. 2004-182923, 2004-214699, 2004-217543, and 2004-218950 filed in Japan, the content of which is incorporated herein by reference.
2. Description of Related Art
An example of a known technology for carrying out time-resolved spectroscopy using a microscope is described below.
According to such a known technology, pulsed laser beams are focused on a subject and fluorescence emission produced at a minute area in the vicinity of the focal point is detected. Then, the energy transfer is measured based on the characteristics of how the fluorescence emission changes over time.
According to this technology, the environment of a fluorescent molecule included in a specimen can be analyzed based on the fact that the fluorescence lifetime of the molecule changes depending on the distance between the fluorescent molecule and other fluorescent molecules.
Recently, in the technical fields of optical communication and physical measurement, optical signals that change within an extremely short period of time on the order of picoseconds (1 ps=10−12 s) to femtoseconds (1 fs=10−15 s) are often used. The change of an optical signal within such an extremely short time period can be observed by a measuring device with excellent time resolution, for example, a time-resolved spectroscopy apparatus such as a time/2D-space conversion optical system.
The time/2D-space conversion optical system includes a diffraction grating, a one-dimensional Fourier transformation optical system, a time-to-frequency conversion filter, and a one-dimensional inverse Fourier transformation optical system.
Observation of an optical signal using such a time/2D-space conversion optical system is carried out as described below.
First, a signal beam having a plane wavefront is incident at an angle on the diffraction grating to obtain a diffracted beam whose propagation direction and spatial phase distribution intersect at an angle equal to the incident angle of the signal beam to the diffraction grating.
Next, Fourier transformation is performed on the horizontal component of the diffracted beam by the one-dimensional Fourier transformation optical system to obtain the spectral distribution of the signal beam as a spatial distribution.
The spectral distribution obtained in such a manner is filtered using the time-to-frequency conversion filter, which is disposed at a position where the spectral distribution is projected, so that the frequency of the extracted frequency components increases sequentially in the vertical direction.
Inverse Fourier transformation is performed on the horizontal components of the filtered lightwave by the one-dimensional inverse Fourier transformation optical system to obtain a lightwave distribution representing time delay in the horizontal direction and the distribution of the extracted spectral components in the vertical direction. A quasi-two-dimensional spectrogram is formed on the plane intersecting with the horizontal direction representing different degrees of time delay in the lightwave distribution.
By emitting a reference transform-limited (TL) pulse wavefront on the plane intersecting with the horizontal direction representing different degrees of time delay in the lightwave distribution so that the plane matches the wave surface of the emitted plane wavefront, an interference pattern caused by the lightwave distribution and the reference TL pulse wavefront is generated on the plane.
The interference pattern generated in such a manner corresponds to the change in intensity of the lightwave distribution over time. Therefore, by analyzing this interference pattern, information on the amplitude and phase of the signal beam to be measured can be obtained.